Natural Selection : Pitzer College Professor Creates an Arboretum to Preserve Only Plants Native to San Gabriel Valley

To the uneducated eye, it looks like an overgrown vacant lot that just happens to be surrounded by a college campus and two busy four-lane streets.

But Pitzer College professor John Rodman and his students are nurturing it toward its natural state, and in the process, they say they are learning about themselves, Southern California and the natural world.

The project began not long after Rodman saw a bulldozer cut across the land to make a soccer field at neighboring Harvey Mudd College. Five years later, Rodman, with the help of Pitzer President Frank Ellsworth and a host of students and volunteers, has created an eight-acre environmental laboratory and arboretum out of what once was a junk-filled lot and former city dump.

To Rodman, this suburban postage stamp of earth in the San Gabriel foothills represents “probably the most endangered ecosystem in Southern California”--a place where chaparral and coastal sage scrub overlap in an alluvial wash. The vegetation there is known as alluvial scrub.

In Ellsworth, Rodman found a champion of the preservation cause. “In the 12 years I’ve been here, I have seen the (native vegetation) from Claremont to Pasadena disappear,” Ellsworth said. “Our arboretum stands in sharp contrast to cement and the massive development that have destroyed (it).”

So, with the blessings of the Pitzer Board of Trustees, Rodman has created a series of displays of California native plants, a manicured desert garden, an herb garden and a citrus grove in honor of Pitzer’s founder, Russell Pitzer, who made his fortune growing citrus. A restored Craftsman-style house, where students and faculty can gather for lunch, coffee or espresso, serves as a formal focus of the arboretum.

The arboretum accounts for nearly a fourth of Pitzer’s tiny campus.

For Rodman, the real soul of the arboretum is the alluvial wash: “the outback,” he calls it, some six acres of scrub where, during the 1950s and 1960s, a city dump was located. Rodman said the dump’s contents were ordinary household trash and construction debris, which seem to pose no significant environmental threat today.

On a recent day, as he slowly moved from plant to plant, Rodman, 57, illustrated how science, history and ecology intersect. Rodman came to ecology via a Harvard education in politics and philosophy, and he spoke of the land and its plants as a living library.

With a sturdy piece of straw he retrieved from the dust, Rodman poked a cottony speck on a prickly pear cactus. A Mercurochrome-colored liquid oozed from the snowy fiber.

“Look at the juices,” he said. “The Indians, before the Spaniards, used them as natural dyes. Then Spaniards became big importers of it.”

Many people, he said, have no interest in plants, ecology or the science of environmental issues. “But if you tell them about how human beings use the plants or how the plants fit into a culture, these networks are more interesting than just botany.”

John Sax, a Pitzer senior, said he has made such connections by working with Rodman in the arboretum and by taking field trips to places such as the Mojave Desert. “It gives me a feeling that I want to do something and that the efforts won’t be fruitless,” said Sax, 22, of Boston. “You begin to see shades of life. You notice more the pieces of the vista and realize you’re part of it too.”

Rodman and his students are in the process of restoring the scrub area by removing the non-native plants that disrupt the ecological balance. To illustrate, Rodman bent down and pulled some leafy green horehound, which can be found in abundance in the San Gabriel Valley.

Unlike native redberry and white sage, plants such as horehound from Europe, the castor bean from Africa, tree tobacco from Central America or even the now-popular eucalyptus from Australia have disrupted the balance in the semi-desert, he said.

In many cases the plants arrived as seeds buried in the hides of sheep or cattle from abroad or even carried in someone’s trouser cuff. Rodman called this “the most pervasive and subtle causes of ecological disruption worldwide,” as native and non-natives plant compete for nutrients and water.

Using a drip-irrigation system, Rodman and his students are nourishing the native plants to the exclusion of the non-natives in the outback.

As he toured the area, he pointed to some of his favorites, including a collection of tiny oaks that he and his students are hoping will make it through the drought. “Boy, this has a lot of fresh, new growth. It really looks nice,” he said, stroking the leaves of a coast live oak. Once, he said, the San Gabriel Valley landscape was filled with them.

Nearby, a butterfly flitted from yellow buds of a pine bush and onto the crimson tiny flowers of a California fuchsia.

He brushed against the aromatic California sage to examine nearby “our most beautiful wildflower,” the mountain penstemon. He opened the penstemon’s purple blossom to reveal inside the white beard around a stamen.

“Watch out,” he said, as a visitor nearly walked into the one native plant that isn’t Rodman’s favorite, poison oak. The prevalence of the plant, he said, indicates the land “has been disturbed by humans,” thus giving the poison oak fertile ground to flourish.

“You’ve got to look at this beauty,” he said, moving toward white sage to sniff its bushy, grayish leaves. “You could get hooked on that.”

He is hooked on all the native plants: elderberry, coffeeberry, scale broom, black sage, lemonade berry and the viny wild cucumber with spiny pods in the shape of sea urchins.

“This is an extraordinary piece of real estate here,” Rodman said. Pulling up a horehound, he explained that some of his students question whether the 740-student Pitzer should be constructing a parking lot and recreational facility adjacent to the arboretum.

But he said the most valuable area has been spared and that he has negotiated hard to ensure the arboretum’s inclusion in the college’s master plan.

Ellsworth, who says the new parking and recreation facility are needed, at the same time said the arboretum is sacrosanct. “I’m not one to speak in absolutes, but the area that is the arboretum will not ever be built on.”

As Rodman puts it: If areas like the Pitzer arboretum are not saved, “we won’t have anything to compare to or even have a reminder of what once was here.”